13 results for “zero crossing”

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Research ArticleOpen accessIn the abstractVoltage Sag Effects on the Process Continuity of a Refinery with Induction Motors LoadsTarek I. ElShennawy, Mahmoud A. El-Gammal, Amr Y. Abou-GhazalaProblem statement: Process continuity of industrial plants (like a refinery) is subjected to several shutdowns due to voltage sags causing large induction motors to trip, either by undervoltage or by overcurrent relays, sometimes by the mechanical protection. These unplanned shutdowns cost the plant tens of thousands of dollars per shutdown in addition to material damage costs, restart charges and any … …American Journal of Applied Sciences, Vol. 6, Issue 8 · 31 Aug 2009 · 7,120 accessesView PDF Cite

Research ArticleOpen accessIn the abstractDetermination of Ibuprofen and Paracetamol in Binary Mixture Using Chemometric-Assisted Spectrophotometric MethodsWafaa S. HassanThree methods are presented for simultaneous determination of ibuprofen and paracetamol without previous separation. The first method depends on first derivative UV spectrophotometry, with zero-crossing measurement. The first derivative amplitudes at 230 and 290 nm were selected for the assay of ibuprofen and paracetamol, respectively. The second method depends on first derivative of the ratio-spectra by measurements of the amplitudes … …American Journal of Applied Sciences, Vol. 5, Issue 8 · 31 Aug 2008 · 8,199 accessesView PDF Cite

Research ArticleOpen accessIn the abstractDetermination of Metoprolol and Felodipine in Binary Mixture Using Chemometric-Assisted Spectrophotometric and High-Performance Liquid Chromatographic-UV MethodsHesham Salem, Ola M. AbdallahFour methods were developed for simultaneous determination of metoprolol and felodipine without previous separation. In the first method both drugs were determined using first derivative UV spectrophotometry, with zero crossing measurement at 222 and 235 nm for metoprolol and felodipine, respectively. The second method depends on first derivative of the ratios spectra by measurements of the amplitudes at 250.1 nm … …American Journal of Applied Sciences, Vol. 4, Issue 9 · 30 Sep 2007 · 8,025 accessesView PDF Cite